Solar Terrestrial Activity Report

Last major update issued on March 30, 2011 at 03:35 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-24 (last update March 2, 2011)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update March 2, 2011)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update March 2, 2011)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update March 1, 2011)]

[POES auroral activity level charts since October 2009 - updated March 28, 2011]
Annotated geomagnetic activity charts - Carrington rotation 2106 [Jan.-Feb.2011] - 2107 [Feb.-March 2011] NEW

Recent activity

The geomagnetic field was quiet to unsettled on March 29. Solar wind speed ranged between 306-387 km/s. A solar wind shock was observed at SOHO at 15:13 UTC. Although solar wind speed didn't increase much, wind density became very high until late in the day. The shock was associated with the partial halo CME observed on March 24 (M1 flare in region 11176). The interplanetary magnetic field was mostly northwards after the shock, with the exeception of a southward excursion 21:30 to 23:10 UTC.

Solar flux estimated at 20h UTC on 2.8 GHz was 116.2 (increasing 2.8 over the last solar rotation). The planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.4). Three hour interval K indices: 00011213 (planetary), 00011212 (Boulder).

The background x-ray flux is at the class B4 level.

At midnight UTC the visible solar disk had 7 spotted regions.

Region 11176 decayed slowly losing some of its smallest spots, there's penumbra only on leading polarity spots. The spots in the region extend longitudinally over 30 degrees (from W03 to W33, however, there is only penumbra at one end of the region.
Region 11178 decayed slowly and was quiet.
Region 11180 was quiet and stable.
Region 11181 was quiet and stable.
Region 11183 didn't change significantly, there's still only minor polarity intermixing. Flares: C1.1 at 05:15 at C1.2 at 21:29 UTC.

Spotted regions not numbered by NOAA/SWPC:
[S920] reemerged on March 27. Location at midnight: S27E05.
[S924] emerged with a couple of tiny spots in an old plage area on March 29. Location at midnight: N35E35.

Another large CME was observed over the east limb after 21:10 UTC in LASCO images.

Coronal mass ejections (CMEs)

March 27-29: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.

Coronal holes

Coronal hole history (since late October 2002)
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago

No obvious coronal holes are currently in or near Earth facing positions.

The darkest areas on the solar disk are likely coronal holes.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over high and upper middle latitudes is poor. Propagation on long distance northeast-southwest paths is poor to fair.

Forecast

The geomagnetic field is expected to be quiet to active on March 30 due to CME effects and quiet on March 31 - April 1.

1) Effects from a coronal hole could reach Earth within the next 5 days. When the high speed stream has arrived the color changes to green.
2) Effects from a CME are likely to be observed at Earth within 96 hours.
3) There is a possibility of either M or X class flares within the next 48 hours.

Green: 0-20% probability, Yellow: 20-60% probability, Red: 60-100% probability.

Active solar regions

(Click on image for higher resolution image) Compare to the previous day's image

When available the active region map has a coronal hole polarity overlay where red (pink) is negative and blue (blue-green) is positive.

Data for all numbered solar regions according to the Solar Region Summary provided by NOAA/SWPC. Comments are my own, as is the STAR spot count (spots observed at or inside a few hours before midnight) and data for regions not numbered by SWPC or where SWPC has observed no spots. SWPC active region numbers in the table below and in the active region map above are the historic SWPC/USAF numbers.

Active region	Date numbered detected	Spot count		Location at midnight	Area	Classification		SDO / HMI 4K continuum image with polarity overlay		Comment
		SWPC	STAR SDO			SWPC	STAR	Current	Previous
11176	2011.03.21	21	29	S16W24	0210	FSI	CSI			beta-gamma location: S17W21
11177	2011.03.21 2011.03.23	4		N19W30	0010	BXO				plage
11178	2011.03.24	6	11	S16E04	0010	BXO	BXO
11181	2011.03.24 2011.03.25	2	4	S25E18	0010	AXX	CRO			location: S28E19
11180	2011.03.24 2011.03.25	1	3	N24E12	0020	HRX	CSO			location: N24E16
11182	2011.03.24 2011.03.27			N13W26						plage
S920	2011.03.25		1	S27E05	0000		AXX
11183	2011.03.26 2011.03.27	14	28	N15E39	0210	EAC	EAC			beta-gamma
S922	2011.03.26			N23W15						plage
S923	2011.03.27			S26E12						plage
S924	2011.03.29		2	N35E35	0000		AXX
Total spot count:		48	78
Sunspot number:		108	148

Monthly solar cycle data

1) Running average based on the daily 20:00 UTC observed solar flux value at 2800 MHz.
2A) Current impact on the monthly sunspot number based on the Boulder (NOAA/SWPC) sunspot number (accumulated daily sunspots / month days). The official SIDC international sunspot number is typically 30-50% lower. 2B) Month average to date.
3) Running average based on the preliminary daily SWPC ap indices. Values in red are based on the official NGDC ap indices.

This report has been prepared by Jan Alvestad. It is based on analysis of data from whatever sources are available at the time the report is prepared. All time references are to the UTC day. Comments and suggestions are always welcome.

SDO images are courtesy of NASA/SDO and the AIA, EVE, and HMI science teams.